Damper of washing machine

Abstract

A damper includes: a cylinder; a piston rod disposed to be movable linearly in the cylinder; and a plurality of damping members installed between the cylinder and the piston rod, and generating a damping force by multi-stage so that when a vibration transmitted from the cylinder to the piston rod or from the piston rod to the cylinder is big, a strong damping force is generated, whereas when a vibration is small, a weak damping force is generated. A damping force is generated by stages depending on a displacement of a vibration transferred from the cylinder to the piston or from the piston to the cylinder. If a small amount of vibration is transferred, a weak damping force is generated, whereas if a large amount of vibration is transferred, a strong damping force is generated. Accordingly, a vibration damping performance can be improved.

What is claimed is:  
     
         1 . A damper for a washing machine comprising: 
 a cylinder connected to one of a tub and a cabinet;    a piston rod connected to the other remaining one of the tub and the cabinet; and    a damping unit installed between the cylinder and the piston rod and generating a damping force in a multi-step to exert a weak damping force when vibration transferred from the cylinder to the piston rod or from the piston rod to the cylinder is small and exerting a strong damping force when vibration transferred from the cylinder to the piston rod or from the piston rod to the cylinder is big.    
     
     
         2 . The damper of  claim 1 , wherein the damping unit comprises: 
 a first damping member mounted at the piston rod and elastically deformed to generate a damping force when a relatively small vibration is generated; and    a second damping member mounted at an outer circumference of the first damping member and generating a damping force by rubbing on the inner circumferential surface of the cylinder when a relatively big vibration is generated.    
     
     
         3 . The damper of  claim 2 , wherein the first damping member is made of a material having an elastic force, of which an inner circumferential surface is insertedly fixed at an engaging unit formed at the piston rod and both sides are disposed to maintain a certain interval from the inner side of the engaging unit formed at the piston rod.  
     
     
         4 . The damper of  claim 3 , wherein both sides of the engaging unit of the piston rod have a sloping side with a predetermined tilt angle (θ1), and the side of the first damping member has a sloping side with a tilt angle (θ2) smaller than the tilt angle (θ1) of the sloping side of the engaging unit.  
     
     
         5 . The damper of  claim 2 , wherein the first damping member is made of a rubber material elastically deformed when a vibration transferred from the cylinder to the piston rod or from the piston rod to the cylinder is smaller than a first displacement value.  
     
     
         6 . The damper of  claim 2 , wherein a support member is installed between the first damping member and the second damping member to fix the second damping member at an outer circumferential surface of the first damping member.  
     
     
         7 . The damper of  claim 6 , wherein an inner circumferential surface of the second damping member is insertedly fixed to the support member, and an outer circumferential surface of the second damping member rubs on a friction surface of the cylinder.  
     
     
         8 . The damper of  claim 7 , wherein the second damping member is made of a grease-absorbed sponge material.  
     
     
         9 . The damper of  claim 1 , wherein the damping unit comprises: 
 a first damping member mounted at the piston rod and exerting a damping force when a vibration smaller than a first displacement value is generated;    a second damping member mounted at an outer circumference of the first damping member and exerting a damping force when a vibration equal to or greater than the first displacement value but smaller than a second displacement value is generated; and    a third damping member mounted at an outer circumference of the second damping member and exerting a damping force when a vibration equal to or greater than the second displacement value is generated.    
     
     
         10 . The damper of  claim 9 , wherein a first support member is fixed between the first damping member and the second damping member, and a second support member is fixed between the second damping member and the third damping member.  
     
     
         11 . The damper of  claim 9 , wherein the first damping member is formed such that its inner circumferential surface fixed at an engaging unit formed at the piston rod and its side is formed as a sloping side with a tilt angle (θ5) smaller than a tilt angle (θ4) of the sloping side of the engaging unit.  
     
     
         12 . The damper of  claim 10 , wherein the second damping member has an inner circumferential surface fixed at the outer circumferential surface of the first support member, an outer circumferential surface fixed at the second support member, and a side formed as a sloping side having a tilt angle (θ6) smaller than a tilt angle (θ7) of the sloping side of the second support member.  
     
     
         13 . The damper of  claim 10 , wherein the first and second damping members are made of a rubber material, and the third damping member is made of a grease-absorbed sponge material.  
     
     
         14 . The damper of  claim 1 , wherein the damping unit comprises: 
 a connection rod connected to a lower end of the piston rod;    a first damping member fixed at the center of a connection rod and generating a damping force by being elastically deformed when a vibration smaller than a pre-set value is transferred; and    a second damping member mounted at both ends of the first damping member, tightly attached to a friction surface of the cylinder in a rubbing-available manner, and generating a damping force by rubbing on the friction surface when a vibration greater than the pre-set value is transferred.    
     
     
         15 . The damper of  claim 14 , wherein first friction member is formed in a plate-spring type which is elastically deformed to absorb a relatively small vibration transferred through the piston rod.  
     
     
         16 . The damper of  claim 14 , wherein a support member is formed at both ends of the first friction member and a second friction member is insertedly coupled to an outer circumferential surface of the support member.  
     
     
         17 . The damper of  claim 1 , wherein the damping unit comprises: 
 a first coil spring-type damping member connected to a lower end of the piston rod and generating a damping force when a vibration smaller than a pre-set value is generated;    a support bar for supporting one end of the other side of the first damping member; and    a second damping member insertedly coupled to both ends of the support bar and tightly attached to the friction surface of the cylinder in a rubbing-available manner.    
     
     
         18 . The damper of  claim 17 , wherein the first damping member is formed as a coil spring having a predetermined elastic force, of which one end is fixed at the piston rod and the other end is fixed at the center of the support bar.  
     
     
         19 . The damper of  claim 1 , wherein the damping unit comprises: 
 a connection rod fixed at a lower end of the piston rod;    a support member into which the connection rod is inserted to be movable linearly;    a first damping member formed as first and second coil springs supported between the support member and the connection rod and exerting a damping force when a vibration smaller than a pre-set value is generated; and    a second damping member fixed at both ends of the support member and generating a damping force by rubbing on the friction surface of the cylinder when a vibration greater than the pre-set value is generated.    
     
     
         20 . The damper of  claim 19 , wherein a through hole is formed at the center of the support member to allow the connection rod to pass therethrough and be movable linearly, and first and second stoppers are formed at the connection rod to support the first damping member, and 
 the first coil spring of the first damping member is supported between one side of the support member and the first stopper formed at the connection rod and the second coil spring of the first damping member is supported between the other side of the support member and the second stopper formed at the connection rod.